1. Technical Field
The present invention relates to a pulp crushing apparatus for crushing a pulp sheet for absorbent product.
2. Description of the Related Art
In manufacturing absorbent products used for hygiene products such as a disposal diaper, conventionally, a crushing apparatus for crushing a pulp sheet is used. Japanese Patent Application Laid Open Gazette No. 2001-309945, for example, discloses a technique to form an absorbent layer of an absorbent product, where a pulp sheet wound on a drum is unreeled and crushed by a crushing apparatus and the crushed pulp is blown on nonwoven fabrics to be layered. In such a crushing apparatus, for crushing pulp sheets, usually, a feed mechanism such as a feed roller feeds the pulp sheets at a constant speed to a crushing cutter which rotates about a rotation axis where the rotation axis is provided in parallel to the pulp sheets and it is orthogonal to a direction of feeding the pulp sheets.
In such a crushing apparatus, however, there is a possibility that a piece of pulp after passing the feed roller might be pulled by and get entangled in the crushing cutter in crushing a rear end portion of the fed pulp sheet, to go in a crushing chamber provided with the crushing cutter, without being crushed. Even if no piece of pulp gets entangled, the movement speed of pulp sheets increases with torque of the crushing cutter and this makes the amount of crushed pulp to be generated in a unit time larger than the regular amount and makes the crushed pulp coarser. Further, since the distance between a rear end portion of a preceding pulp sheet and a following pulp sheet becomes larger for a certain interval and no crushed pulp is generated for the interval, there arises variation in the amount of crushed pulp to be generated in a unit time and quality thereof, and therefore the uniformity in quality of an absorbent product to be formed is disadvantageously degraded.
For this reason, an operation of stopping the apparatus before entangling the rear end portion of the pulp sheet to remove it from the feed roller is needed and this decreases the efficiency of crushing operation and makes improvement in yield difficult. With two pulp feed mechanisms alternately working, a decrease in efficiency of the crushing operation can be prevented but the apparatus disadvantageously becomes larger.
The coarsely crushed pulp is repeatedly crushed until it becomes smaller than a predetermined size by providing a screen with a lot of very small openings at an outlet of the crushing chamber for discharging the crushed pulp and another crushing mechanism in the crushing chamber, or a full stop of generation of the crushed pulp is prevented by parallelly using a crushing apparatus for crushing a pulp sheet coarsely and another crushing apparatus for crushing a pulp sheet finely. These methods, however, can not keep a constant amount of crushed pulp to be generated in a unit time and thereby need measurement for the amount of crushed pulp before formation of an absorbent product.